High Availability for VM runner docs

[SushrutHarness]

Thanks for contributing to the Harness Developer Hub! Our code owners will review your submission.

Description

• Please describe your changes: __________________________________
• Jira/GitHub Issue numbers (if any): ______________________________
• Preview links/images (Internal contributors only): __________________

PR lifecycle

We aim to merge PRs within one week or less, but delays happen sometimes.

If your PR is open longer than two weeks without any human activity, please tag a code owner in a comment.

PRs must meet these requirements to be merged:

• Successful preview build.
• Code owner review.
• No merge conflicts.
• Release notes/new features docs: Feature/version released to at least one prod environment.

[bot-gitexp-user]

Please check the Execution Link of the Pipeline for the Website Draft URL. This is located in the Preview Step behind the Harness VPN and also is available in #hdh_alerts. E.g Website Draft URL: https://unique-id--harness-developer.netlify.app. Current Draft URL is: https://6838d8edbc5b92e23db1d7f2--harness-developer.netlify.app

[devkimittal]

Can we please include documentation for RUNNER_URL variable as well? I just had a customer call where they were not able to find it. Basically delegate by default looks for runner on localhost:3000 url. We can override it with flag RUNNER_URL, similar to what we have documented for local runner https://developer.harness.io/docs/continuous-integration/use-ci/set-up-build-infrastructure/define-a-docker-build-infrastructure/#install-the-delegate-2

[bot-gitexp-user]

Please check the Execution Link of the Pipeline for the Website Draft URL. This is located in the Preview Step behind the Harness VPN and also is available in #hdh_alerts. E.g Website Draft URL: https://unique-id--harness-developer.netlify.app. Current Draft URL is: https://6849fc2afdf9f8371e2d5aa0--harness-developer.netlify.app

[dewan-ahmed]

@SushrutHarness HA_Archi... file name needs to be changed to satisfy the kebab-case-master